1. Field of the Invention
The present invention relates to a torque calculation apparatus and a torque calculation method of a variable capacitance compressor provided in a refrigeration cycle of a vehicular air conditioning system.
2. Description of the Related Art
In a variable capacitance compressor of this kind, discharge capacity of refrigerant can be varied by an external control signal to save power. If the discharge capacity of the refrigerant is varied, since load acting on an engine is varied, it is necessary that the engine controller controls the intake airflow (fuel supply amount) to prevent engine stalls and idling of the engine in an idling mode. Since the engine controller performs such a control, it is necessary to recognize torque of the variable capacitance compressor. There are conventionally proposed various torque calculation apparatuses. The present applicant previously proposed a torque calculation apparatus having high estimation precision (Japanese Patent Application Laid-open No. 2003-278660).
The torque calculation apparatus of the variable capacitance compressor includes an interior wind amount calculator which calculates an interior wind amount of air flowing into a passenger room through an evaporator, an evaporator air heat absorption amount calculator which calculates an evaporator air heat absorption amount from variations of the interior wind amount and of enthalpy between upstream and downstream of the evaporator, a refrigerant flow rate calculator which calculates a refrigerant flow rate flowing through the evaporator from variations of the evaporator air heat absorption amount and the upstream and downstream of the evaporator, and a compressor drive torque calculator which calculates torque of the compressor using the calculated refrigerant flow rate.
This torque calculation apparatus can calculate torque with high estimation precision by taking the refrigerant flow rate flowing through the evaporator of the refrigeration cycle into consideration.